Wireless Charging Package with Chip Integrated in Coil Center

ABSTRACT

A package includes a device die, and an encapsulating material encapsulating the device die therein. The encapsulating material has a top surface coplanar with a top surface of the device die. A coil extends from the top surface to a bottom surface of the encapsulating material, and the device die is in the region encircled by the coil. At least one dielectric layer is formed over the encapsulating material and the coil. A plurality of redistribution lines is in the at least one dielectric layer. The coil is electrically coupled to the device die through the plurality of redistribution lines.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a continuation of U.S. patent application Ser. No.15/700,926, entitled “Wireless Charging Package with Chip Integrated inCoil Center,” filed on Sep. 11, 2017, which is a continuation of U.S.patent application Ser. No. 15/169,838, entitled “Wireless ChargingPackage with Chip Integrated in Coil Center,” filed on Jun. 1, 2016, nowU.S. Pat. No. 9,761,522 issued Sep. 12, 2017, which application claimsthe benefit of the following provisionally filed U.S. Patentapplication: Application No. 62/288,831, filed Jan. 29, 2016, andentitled “InFO_WC with Chip Integrated in Coil Center,” whichapplications are hereby incorporated herein by reference.

BACKGROUND

Wireless charging has become an increasingly popular chargingtechnology. Wireless charging is sometimes known as inductive charging,which uses an electromagnetic field to transfer energy between an energytransmitter and an energy receiver. The Energy is sent through inductivecoupling to an electrical device, which can then use that energy tocharge batteries or run the device. Induction chargers use a firstinduction coil to create an alternating electromagnetic field from thetransmitter and a second induction coil to receive the power from theelectromagnetic field. The second induction coil converts the energyback into electric current, which is then used to charge a battery ordirectly drive electrical devices. The two induction coils, whenproximal to each other, form an electrical transformer.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1 through 14 illustrate the cross-sectional views of intermediatestages in the formation of some packages in accordance with someembodiments.

FIG. 15 illustrates a top view of a package in accordance with someembodiments.

FIG. 16 illustrates a process flow for forming a package in accordancewith some embodiments.

FIG. 17 illustrates a portion of the coil in accordance with someembodiments.

FIG. 18 illustrates a double-line coil in accordance with someembodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “underlying,” “below,”“lower,” “overlying,” “upper” and the like, may be used herein for easeof description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

A package for wireless charging, which includes an AC-DC convertercircuit chip and/or a Bluetooth circuit chip, is provided in accordancewith various exemplary embodiments. The intermediate stages of formingthe package are illustrated. Some variations of some embodiments arediscussed. Throughout the various views and illustrative embodiments,like reference numbers are used to designate like elements.

FIGS. 1 through 14 illustrate the cross-sectional views of intermediatestages in the formation of some packages in accordance with someembodiments of the present disclosure. The steps shown in FIG. 1 through14 are also schematically illustrated in the process flow 200 shown inFIG. 16.

FIG. 1 illustrates carrier 20 and release layer 22 formed over carrier20. Carrier 20 may be a glass carrier, a ceramic carrier, or the like.Carrier 20 may have a round top-view shape, and may have a size of asilicon wafer. For example, carrier 20 may have an 8-inch diameter, a12-inch diameter, or the like. Release layer 22 may be formed of apolymer-based material (such as a Light To Heat Conversion (LTHC)material), which may be removed along with carrier 20 from the overlyingstructures that will be formed in subsequent steps. In accordance withsome embodiments of the present disclosure, release layer 22 is formedof an epoxy-based thermal-release material. In accordance with someembodiments of the present disclosure, release layer 22 is formed of anultra-violet (UV) glue. Release layer 22 may be dispensed as a liquidand cured. In accordance with alternative embodiments of the presentdisclosure, release layer 22 is a laminate film and is laminated ontocarrier 20. The top surface of release layer 22 is leveled and has ahigh degree of co-planarity.

In accordance with some embodiments of the present disclosure,dielectric layer 24 is formed over release layer 22. The respective stepis shown as step 202 in the process flow shown in FIG. 16. In the finalproduct, dielectric layer 24 may be used as a passivation layer toisolate the overlying metallic features from the adverse effect ofmoisture and other detrimental substances. Dielectric layer 24 may beformed of a polymer, which may also be a photo-sensitive material suchas polybenzoxazole (PBO), polyimide, benzocyclobutene (BCB), or thelike. In accordance with alternative embodiments of the presentdisclosure, dielectric layer 24 is formed of an inorganic material(s),which may be a nitride such as silicon nitride, an oxide such as siliconoxide, PhosphoSilicate Glass (PSG), BoroSilicate Glass (BSG),Boron-doped PhosphoSilicate Glass (BPSG), or the like. In accordancewith yet alternative embodiments of the present disclosure, nodielectric layer 24 is formed. Accordingly, dielectric layer 24 is shownwith dashed lines to indicate that it may or may not be formed.

FIGS. 2 and 3 illustrate the formation of conductive features 32, whichare referred to as through-conductors hereinafter since they penetratethrough the encapsulation material 52 (FIG. 6) that will be dispensed insubsequent steps. Referring to FIG. 2, seed layer 26 is formed overdielectric layer 24, for example, through Physical Vapor Deposition(PVD) or metal foil lamination. Seed layer 26 may be formed of copper,aluminum, titanium, or multi-layers thereof. In accordance with someembodiments of the present disclosure, seed layer 26 includes a titaniumlayer (not separately shown) and a copper layer (not separately shown)over the titanium layer. In accordance with alternative embodiments,seed layer 26 includes a single copper layer.

Photo resist 28 is applied over seed layer 26 and is then patterned. Therespective step is also shown as step 202 in the process flow shown inFIG. 16. As a result, openings 30 are formed in photo resist 28 bylight-exposure and development steps. Some portions of seed layer 26 areexposed through openings 30.

In accordance with some embodiments of the present disclosure, openings30 are used for forming coil 33 (FIG. 15), which may be used as areceiver for receiving energy in wireless charging. To improve theefficiency of receiving energy, the pitch P1 of openings 30 is designedand implemented to be as small as possible. For example, in accordancewith some embodiments of the present application, pitch P1 is smallerthan about 300 μm. As shown in FIG. 15, coil 33 has four sides, eachbeing very long (compared to its widths). Furthermore, as shown in FIG.13, conductors 32, which in combination form coil 33 as in FIG. 15, havehigh aspect ratios. Accordingly, it is difficult to form a long, narrow,and low-pitch coil. In accordance with some embodiments of the presentapplication, photo resist 28 is selected according to the design of coil33 such as the shape, the size, the height (in the cross-sectional viewas in FIG. 13), and the size and the shape of the region encircled bycoil 33. An exemplary method of finding proper photo resist materialincludes determining the resolution of a plurality of candidate photoresist materials, using matrix evaluation to determine the resolution ofthe candidate photo resist materials, finding appropriate photo resistsfrom the candidate photo resist materials that have the desirableresolution, and then performing experiments to test which of theselected photo resists can meet the design requirement. It is realized,however, that the type of proper photo resist material is related tovarious factors as discussed, and a photo resist suitable for one designmay not be suitable for other designs.

Referring back to FIG. 1, with photo resist 28 being formed of a propermaterial, the pitch P1 of openings 30 may be low enough, so that theoverall efficiency of coil 33 for receiving energy may be high enough tomeet design requirement. In accordance with some embodiments of thepresent disclosure, openings 30 have widths W1 smaller than about 300μm, and spacing S1 between neighboring openings 30 may also be smallerthan about 300 μm. Accordingly, pitch P1 may be smaller than about 600μm.

Next, as also shown in FIG. 2, through-conductors 32 are formed inopenings 30 through plating, which may be electro plating orelectro-less plating. The respective step is shown as step 204 in theprocess flow shown in FIG. 16. Through-conductors 32 are plated on theexposed portions of seed layer 26. Through-conductors 32 may includecopper, aluminum, tungsten, nickel, or alloys thereof. The top-viewshapes of through-conductors 32 include, and are not limited to,spirals, rings, rectangles, squares, circles, and the like, depending onthe intended function of through-conductors 32 and available space. Theheights of through-conductors 32 are determined by the thickness of thesubsequently placed integrated circuit chips (device dies) 38 (FIG. 5,including 38A and 38B), with the heights of through-conductors 32 beinggreater than or equal to the thicknesses of device dies 38 in accordancewith various embodiments.

After the plating of through-conductors 32, photo resist 28 is removed,and the resulting structure is shown in FIG. 3. The portions of seedlayer 26 (FIG. 2) that were previously covered by photo resist 28 areexposed. An etch step is then performed to remove the exposed portionsof seed layer 26, wherein the etching may be an anisotropic or isotropicetching. The portions of seed layer 26 that are overlapped bythrough-conductors 32, on the other hand, remain not etched. Throughoutthe description, the remaining underlying portions of seed layer 26 areconsidered as being the bottom portions of through-conductors 32. Whenseed layer 26 is formed of a material similar to or the same as that ofthe respective overlying through-conductors 32, seed layer 26 may bemerged with through-conductors 32 with no distinguishable interfacetherebetween. Accordingly, seed layers 26 are not shown in subsequentdrawings. In accordance with alternative embodiments of the presentdisclosure, there exist distinguishable interfaces between seed layer 26and the overlying plated portions of through-conductors 32.

The top-view shape of through-conductors 32 is related to, and isdetermined by, their intended function. In accordance with someexemplary embodiments in which through-conductors 32 are used to form aninductor, the illustrated through-conductors 32 may be a part of coil33. FIG. 15 illustrates the top view of an exemplary inductor inaccordance with some exemplary embodiments. In FIG. 15,through-conductors 32 in combination form a spiral, with two ports 34connected to the opposite ends of the spiral. In accordance withalternative embodiments (not shown), through-conductors 32 form aplurality of concentric rings, with the outer rings encircling the innerrings. The rings have breaks to allow the outer rings to be connected tothe inner rings through bridges, and the plurality of rings is seriallyconnected to two ports 34. Ports 34 are also connected to semiconductorchip 38A.

FIG. 4 illustrates the placement of device dies 38 (including 38A and38B) over carrier 20. The respective step is shown as step 206 in theprocess flow shown in FIG. 16. Device dies 38 may be adhered todielectric layer 24 through Die-Attach Films (DAF) 40, which areadhesive films. In accordance with some embodiments of the presentdisclosure, device dies 38 include AC-DC converter chip 38A, which hasthe function of receiving the AC current from coil 33, and convertingthe AC current to a DC current. The DC current is used to charge abattery (not shown), or to drive circuits of the respective product, inwhich the package including coil 33 is located.

Device dies 38 may also include communication die 38B, which may beBluetooth Low-Energy (BLE) die. BLE die 38B may have the function ofcommunicating with a transmitter (not shown), for example, throughBluetooth technology. The transmitter and BLE die 38B may negotiate thetransmission of energy, for example, when the distance between thetransmitter and coil 33 is small enough, and/or when the stored power inthe battery is lower than a pre-determined threshold level. Thetransmitter may than start transmitting energy, which may be in the formof magnetic field at a high frequency, for example, at about 6.78 MHz.Coil 33 receives the energy, and feed the respective current to AC-DCconverter chip 38A.

In accordance with some embodiments of the present disclosure, theformation of the package is at wafer-level. Accordingly, a plurality ofcoils 33 is formed simultaneously, each encircling an inner region. Aplurality of device dies 38 is placed on carrier 20. For example, eachof the coils 33 encircles one device die 38A and one device die 38Btherein. The plurality of coils 33 and device dies 38 are allocated asan array having a plurality of rows and columns.

Device dies 38 may include semiconductor substrates 42A and 42B,respectively, which may be silicon substrates. Integrated circuitdevices 44A and 44B are formed on semiconductor substrates 42A and 42B,respectively. Integrated circuit devices 44A and 44B include activedevices such as transistors and diodes, and may or may not includepassive devices such as resistors, capacitors, inductors, or the like.Device dies 38 may include metal pillars 46 electrically coupled to therespective integrated circuit devices 44A and 44B. Metal pillars 46 maybe embedded in dielectric layer 48, which may be formed of PBO,polyimide, or BCB, for example. Passivation layers 50 are alsoillustrated, wherein metal pillars 46 may extend into passivation layers50. Passivation layers 50 may be formed of silicon nitride, siliconoxide, or multi-layers thereof.

Next, referring to FIG. 5, encapsulating material 52 is encapsulated(sometimes referred to as molded) on device dies 38. The respective stepis shown as step 208 in the process flow shown in FIG. 16. Encapsulatingmaterial 52 fills the gaps between neighboring through-conductors 32 andthe gaps between through-conductors 32 and device dies 38. Encapsulatingmaterial 52 may include a polymer-based material, and may include amolding compound, a molding underfill, an epoxy, and/or a resin. The topsurface of encapsulating material 52 is higher than the top ends ofmetal pillar 46.

In a subsequent step, as shown in FIG. 6, a planarization process suchas a Chemical Mechanical Polish (CMP) process or a grinding process isperformed to reduce the top surface of encapsulating material 52, untilthrough-conductors 32 and metal pillar 46 are exposed. The respectivestep is shown as step 210 in the process flow shown in FIG. 16. Due tothe planarization, the top ends of through-conductors 32 aresubstantially level (coplanar) with the top surfaces of metal pillars46, and are substantially coplanar with the top surface of encapsulatingmaterial 52.

In accordance with some embodiments of the present disclosure, devicedies 38 are embedded in encapsulating material 52, as shown in FIG. 6.Passive devices 56 (marked as 56A) may also be placed on carrier 20before the encapsulation step as shown in FIG. 5. The respective passivedevices 56 are shown in FIG. 14, which also illustrates more featuresformed in subsequent steps. Passive devices 56A may be capacitors,resistors, inductors, and/or the like. The surface conductive features46 of passive devices 56A are also exposed in the planarization step asshown in FIG. 6. Accordingly, passive devices 56A are electricallycoupled to other devices through the subsequently formed RedistributionLines (RDLs). Passive devices 56A may be Integrated Passive Devices(IPDs), which are formed on semiconductor substrates in the respectivechips. Throughout the description, an IPD may be a single-device chip,which may include a single passive device such as an inductor, acapacitor, a resistor, or the like, with no other passive devices andactive devices in the respective chip. Furthermore, in accordance withsome embodiments, there are no active devices such as transistors anddiodes in IPDs 56A.

In accordance with alternative embodiments, there is no passive deviceencapsulated in encapsulating material 52. Accordingly, in FIG. 14,passive devices 56A are illustrated using dashed lines to indicatepassive devices may be or may not be embedded in encapsulating material52.

FIGS. 7 through 11 illustrate the formation of front-side RDLs and therespective dielectric layers. Referring to FIG. 7, dielectric layer 54is formed. The respective step is shown as step 212 in the process flowshown in FIG. 16. In accordance with some embodiments of the presentdisclosure, dielectric layer 54 is formed of a polymer such as PBO,polyimide, or the like. In accordance with alternative embodiments ofthe present disclosure, dielectric layer 54 is formed of an inorganicmaterial such as silicon nitride, silicon oxide, or the like. Openings57 are formed in dielectric layer 54 (for example, through exposure anddevelopment) to expose through-conductors 32 and metal pillars 46.Openings 57 may be formed through a photo lithography process.

Next, referring to FIG. 8, Redistribution Lines (RDLs) 58 are formed toconnect to metal pillars 46 and through-conductors 32. The respectivestep is shown as step 214 in the process flow shown in FIG. 16. RDLs 58may also interconnect metal pillars 46 and through-conductors 32. Inaddition, RDLs 58 may be used to form the connection for connectingports 34 (FIG. 15) of inductor 33 to device die 38A. RDLs 58 includemetal traces (metal lines) over dielectric layer 54 and vias extendinginto dielectric layer 54. The vias in RDLs 58 are connected tothrough-conductors 32 and metal pillars 46. In accordance with someembodiments of the present disclosure, the formation of RDLs 58 includesforming a blanket copper seed layer, forming and patterning a mask layerover the blanket copper seed layer, performing a plating to form RDLs58, removing the mask layer, and etch the portions of the blanket copperseed layer not covered by RDLs 58. RDLs 58 may be formed of a metal or ametal alloy including aluminum, copper, tungsten, and/or alloys thereof.

Referring to FIG. 9, in accordance with some embodiments of the presentdisclosure, dielectric layer 60 is formed over the structure shown inFIG. 8, followed by the formation of openings 62 in dielectric layer 60.Some portions of RDLs 58 are thus exposed. The respective step is shownas step 216 in the process flow shown in FIG. 16. Dielectric layer 60may be formed using a material selected from the same candidatematerials for forming dielectric layer 54.

Next, as shown in FIG. 10, RDLs 64 are formed in dielectric layer 60.The respective step is also shown as step 216 in the process flow shownin FIG. 16. In accordance with some embodiments of the presentdisclosure, the formation of RDLs 64 includes forming a blanket copperseed layer, forming and patterning a mask layer over the blanket copperseed layer, performing a plating to form RDLs 64, removing the masklayer, and etching the portions of the blanket copper seed layer notcovered by RDLs 64. RDLs 64 may also be formed of a metal or a metalalloy including aluminum, copper, tungsten, and/or alloys thereof. It isappreciated that although in the illustrated exemplary embodiments, twolayers of RDLs (58 and 64) are formed, the RDLs may have any number oflayers such as one layer or more than two layers. The RDLs incombination may electrically interconnect through-conductors 32, devicedies 38, passive devices 56, and the like.

FIGS. 11 and 12 illustrate the formation of dielectric layer 66 andelectrical connectors 68 in accordance with some exemplary embodiments.The respective step is shown as step 218 in the process flow shown inFIG. 16. Referring to FIG. 11, dielectric layer 66 is formed, forexample, using PBO, polyimide, or BCB. Openings 59 are formed indielectric layer 66 to expose the underlying metal pads, which are partsof RDLs 64. In accordance with some embodiment, Under-Bump Metallurgies(UBMs, not shown) are formed to extend into opening 59 in dielectriclayer 66.

Electrical connectors 68 are then formed, as shown in FIG. 12. Theformation of electrical connectors 68 may include placing solder ballson the exposed portions of the UBMs, and then reflowing the solderballs. In accordance with alternative embodiments of the presentdisclosure, the formation of electrical connectors 68 includesperforming a plating step to form solder regions over the exposed metalpads in RDLs 64, and then reflowing the solder regions. Electricalconnectors 68 may also include metal pillars, or metal pillars andsolder caps, which may also be formed through plating. Throughout thedescription, the structure including dielectric layer 24 and theoverlying structure in combination is referred to as package 100, whichis a composite wafer including a plurality of device dies 38.

Next, package 100 is de-bonded from carrier 20, for example, byprojecting a UV light or a laser beam on release layer 22, so thatrelease layer 22 decomposes under the heat of the UV light or the laserbeam. Package 100 is thus de-bonded from carrier 20. The resultingpackage 100 is shown in FIG. 13. In accordance with some embodiments ofthe present disclosure, in the resultant package 100, dielectric layer24 remains as a bottom part of package 100, and protectsthrough-conductors 32. Dielectric layer 24 may be a blanket layer withno through-opening therein. In accordance with alternative embodiments,dielectric layer 24 is not formed, and the bottom surfaces ofencapsulating material 52 and through-conductors 32 are exposed afterthe de-bonding. A backside grinding may (or may not) be performed toremove DAFs 40, if they are used, so that the bottom surfaces ofthrough-conductors 32 are coplanar with the bottom surfaces of devicedies 38A and 38B. The bottom surface of device dies 38A and 38B may alsobe the bottom surfaces of semiconductor substrates 42A and 42B.

FIG. 14 illustrates the bonding of passive devices 56B to package 100.The respective step is shown as step 220 in the process flow shown inFIG. 16. In FIG. 14, passive devices 56B overlap device dies 38A and38B. Some passive devices 56B may also overlap passive devices 56A.Passive devices 56B are also referred to as surface-mount devices sincethey are mounted on the top surface of package 100. Passive devices 56Bmay be capacitors, resistors, inductors, and/or the like. Passivedevices 56B may be IPDs formed on semiconductor substrates. Furthermore,in accordance with some embodiments, there are no active devices such astransistors and diodes in passive devices 56B. In accordance with someembodiments, either embedded passive devices 56A, surface-mountedpassive devices 56, or both, are adopted in package 100. Accordingly,passive devices 56A and 56B are shown as dashed to indicate they may ormay not be formed. Embedding passive devices 56A or bonding passivedevices 56B on top of RDLs have their own advantageous features. Forexample, when passive devices 56A are adopted while no passive devices56B are bonded, the total thickness of package 100 may be reduced. Onthe other hand, bonding passive devices 56B may reduce the area ofpackage 100. Accordingly, either the embedded passive devices 56A, thesurface-mounted passive devices 56B, or both, are adopted in package 100to suit to different design requirements. Passive devices 56A and 56Bmay be electrically coupled to device dies 38A and/or 38B through RDLs64 and 58.

Package 100 is then singulated in accordance with some embodiments ofthe present disclosure, and package 100 is sawed into a plurality ofpackages 100′ that is identical to each other. FIG. 15 illustrates a topview of an exemplary package 100′. In accordance with some exemplaryembodiments, package 100′ includes four edges 100A. The cross-sectionalview shown in FIG. 13 is obtained from the plane containing line 13-13in FIG. 15. The cross-sectional view shown in FIG. 14 is obtained fromthe plane containing line 14-14 in FIG. 15. Inductor 33 has four sidesthat are proximal to the respective edges 100A. Furthermore, there maynot be any device located between inductor 33 and edges 100A. Ports 34of inductor 33 are connected to device die 38A through RDLs 58/64.Device dies 38A and 38B are encircled by coil 33 (and the respectivethrough-conductors 32), wherein no device die and no passive device isoutside of coil 33, so that the area of package 100′ is minimized.Passive devices 56 (including 56A and/or 56B) are also encircled by (inthe top view of package 100′) inductor 33. Referring to FIG. 15, inaccordance with some embodiments, length L1 of coil 33 (which is thelongest length of the concentric rings) is in the range between about50% and about 99% of length L2 of package 100′ (which is also the lengthof encapsulating material 52). The shortest length L3 of the concentricrings is about 30% to about 70% of length L2. The occupied area of coil33 (including the central area surrounded by coil 33) may be betweenabout 25% and about 98% of the top-view area of package 100′. The ratioof width W1/H1 (FIG. 14) may be in the range between about 0.4 and about1.5.

FIG. 14 also illustrates seal ring 70 formed in dielectric layers 54, 60and 66. Seal ring 70 is formed simultaneously as the formation of RDLs58 and 64. In a top view of package 100′, seal ring 70 encircles coil33, and is formed between coil 33 and the respective edges of package100′ (FIG. 15, wherein seal ring 70 is not shown). Seal ring 70 may beelectrically grounded or electrically floating.

FIG. 17 illustrates an amplified view of portion 72 of package 100′ inFIG. 15, wherein two through-conductors 32 are illustrated as anexample. To reduce stress, through-conductors 32 may have roundedcorners. For example, the radius R1 of through conductors may be in therange between about W1/2 and 2W1/3.

To enhance the efficiency, the outer rings of coil 33 may have widthsgreater than or equal to the width of the widths of the inner rings inaccordance with some embodiments. For example, referring to FIG. 15,width W1A, which may be the width of the outmost ring, may be equal toor greater than width W1B of the innermost ring. Ratio W1B/W1A may be inthe range between about 1/2 and about 2/3. Furthermore, from outer ringsto the inner rings, the widths of through-conductors 32 may beincreasingly reduced or periodically reduced every several rings.

FIG. 18 illustrates package 100′ including a double-line coil 33 inaccordance with some embodiments. For a clearer view, RDLs 58 and 64(FIG. 15) that connect the ends of coil 33 to device die 38A are notillustrated in FIG. 18. The structure in FIG. 18 is essentially the sameas shown in FIG. 15, except that coil 33, instead of having a singlethrough-conductor 32 coiling, has two through-conductors 32A and 32Bcoiling in parallel. Through-conductors 32A and 32B are parallel to eachother, and are in combination used like a single conductor to form coil.In order to distinguish through-conductors 32A from 32B, so that theirlayouts can be clearly seen, through-conductors 32A and 32B are shownusing different patterns.

As shown in FIG. 18, each of through-conductors 32A and 32B by itselfforms a coil. The ends of through-conductors 32A and 32B areinterconnected through connectors 74A and 74B. Each of connectors 74Aand 74B may be a through-via formed simultaneously whenthrough-conductors 32A and 32B are formed, or may be a part of RDLs 58and 64. Connectors 74A and 74B may also include both thethrough-conductor portion and the RDL portion. In accordance with someembodiments, through-conductors 32A and 32B are only connected at theirends, but not in the middle, as shown in FIG. 18. In accordance withalternative embodiments, additional connectors similar to connectors 74Aand 74B may be formed periodically to interconnect the middle portionsof through-conductor 32A to the respective middle portions ofthrough-conductor 32A. For example, each straight portion ofthrough-conductors 32A and 32B may include one or more interconnector.

As a result of the interconnection of through-conductors 32A and 32B,through-conductors 32A and 32B in combination form the coil. Whenoperated at a high frequency, for example, several megahertz or higher,coil 33 in FIG. 18 has the performance comparable to, and sometimesbetter than, bulk coil 33 as shown in FIG. 15. This may be caused byskin effect. Furthermore, with through-conductors 32A and 32B beingnarrower compared to a bulk coil since it is equivalent to removing amiddle part of through-conductor 32 as shown in FIG. 15, the patternloading effect in the plating of through-conductors 32A and 32B isreduced.

The embodiments of the present disclosure have some advantageousfeatures. By embedding (active) device dies and embedding and/or bondingpassive devices (dies) in the region encircled by the inductor, the areaof the wireless charger is reduced. It is realized that conventionally,device dies and passive devices cannot be placed inside the inductorsince this will cause the loss of the efficiency of power receiving toan unacceptable level. In accordance with some embodiments of thepresent disclosure, by reducing the pitch of inductor 33, the receivingefficiency if improved, which compensates for the loss in the efficiencycaused by placing device dies and passive device in the region encircledby the inductor. The receiving efficiency is thus increased to anacceptable level.

In accordance with some embodiments of the present disclosure, a packageincludes a device die, and an encapsulating material encapsulating thedevice die therein. The encapsulating material has a top surfacecoplanar with a top surface of the device die. A coil extends from thetop surface to a bottom surface of the encapsulating material, and thedevice die is in the region encircled by the coil. At least onedielectric layer is formed over the encapsulating material and the coil.A plurality of redistribution lines is in the at least one dielectriclayer. The coil is electrically coupled to the device die through theplurality of redistribution lines.

In accordance with some embodiments of the present disclosure, a packageincludes a coil extending to proximal all edges of the package, a devicedie inside the coil, an encapsulating material encapsulating the devicedie and the coil therein, at least one dielectric layer over theencapsulating material and the coil, and a plurality of redistributionlines in the at least one dielectric layer. The plurality ofredistribution lines is electrically coupled to the coil and the devicedie.

In accordance with some embodiments of the present disclosure, a methodincludes forming a coil over a carrier, and placing a device die overthe carrier, wherein the device die is in a region encircled by thecoil. The method further includes encapsulating the device die and thecoil in an encapsulating material, planarizing a top surface of thefirst device die and a top end of the coil with a top surface of theencapsulating material, forming at least one dielectric layer over theencapsulating material, the coil, and the first device die, and forminga plurality of redistribution lines in the at least one dielectriclayer. The plurality of redistribution lines is electrically coupled tothe first device die and the coil.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A package of integrated circuits, the packagecomprising: a coil comprising a plurality of portions, wherein theplurality of portions comprise: a first portion comprising a first edge;a second portion comprising a second edge; and a curved portioncomprising a curved edge, wherein the first edge is connected to thesecond edge through the curved edge; a device die encircled by the coil;and a molding compound encapsulating the coil therein.
 2. The package ofclaim 1, wherein the curved edge has a radius, and the first portion hasa width, and wherein a ratio of the radius to the width is in a rangebetween about 1/3 and about 2/3.
 3. The package of claim 1 furthercomprising a dielectric layer, wherein a bottom surface of thedielectric layer contacts both top surfaces of the plurality of portionsof the coil and a top surface of the molding compound.
 4. The package ofclaim 1, wherein bottom surfaces of the plurality of portions of thecoil are coplanar with a bottom surface of the molding compound.
 5. Thepackage of claim 1, wherein the curved portion has an inner edge and anouter edge, and the curved edge is the outer edge.
 6. The package ofclaim 1, wherein the device die is encapsulated by the molding compound,and a top surface of the device die is coplanar with a top surface ofthe molding compound.
 7. The package of claim 1, wherein in across-sectional view of the coil, the coil comprises a portion havingopposite sidewalls contacting the molding compound, and the portion ofthe coil has a width and a height, and a ratio of the width to theheight is in a range between about 0.4 and about 1.5.
 8. A package ofintegrated circuits, the package comprising: a device die comprising: atop surface and a bottom surface; and a first conductive feature and asecond conductive feature at the top surface; a coil comprising aplurality of portions connected to form a spiral, wherein the spiralcomprises a first end and a second end connecting to the firstconductive feature and the second conductive feature, respectively, andthe coil encircles the device die; and an encapsulating materialencapsulating the coil and the device die therein, wherein theencapsulating material contacts both the device die and the coil.
 9. Thepackage of claim 8, wherein the coil has rounded corners.
 10. Thepackage of claim 9, wherein radii of the rounded corners are in a rangebetween about one third and two thirds of widths of the plurality ofportions.
 11. The package of claim 8, wherein the spiral rotatesrelative to an axis, and the axis is perpendicular to the top surface ofthe device die.
 12. The package of claim 8 further comprising adielectric layer overlapping and contacting both the device die and theencapsulating material, wherein a bottom surface of the dielectric layercontacts both the device die and the encapsulating material.
 13. Thepackage of claim 8, wherein in a top view of the package, the coil has afirst length, and the package has a second length measured in a samedirection as the first length, and a ratio of the first length to thesecond length is in a range between about 0.5 and about 0.99.
 14. Thepackage of claim 8, wherein the coil comprises a double-line coil.
 15. Amethod of forming an integrated circuit package, the method comprising:forming a coil over a carrier; placing a device die over the carrier,wherein the device die is in a region encircled by the coil; andencapsulating the device die and the coil in an encapsulating material.16. The method of claim 15 further comprising performing a singulationalong outer edges of the coil to form a discrete package comprising thecoil and the device die, wherein in the discrete package, no device dieis between the outer edges of the coil and edges of the discretepackage.
 17. The method of claim 15 further comprising: planarizing atop surface of the device die, a top end of the coil, and a top surfaceof the encapsulating material.
 18. The method of claim 15 furthercomprising: forming a dielectric layer over the encapsulating material,the coil, and the device die; and forming a plurality of redistributionlines extending into the dielectric layer to electrically couple to boththe device die and the coil.
 19. The method of claim 18 furthercomprising bonding an integrated passive device over and electricallycoupling to the plurality of redistribution lines, wherein in a top viewof the plurality of redistribution lines, the integrated passive deviceis encircled by the coil.
 20. The method of claim 15, wherein an axis ofthe coil is perpendicular to a major bottom surface of the device die.